LibJS: Remove reduntant set_prototype() calls

If we're inheriting from Object() we already call its constructor which
sets the prototype - no need to do it again.

Libraries/LibJS/Runtime/Error.cpp

@@ -41,7 +41,6 @@ Error::Error(const FlyString& name, const String& message, Object& prototype)
     , m_name(name)
     , m_message(message)
 {
-    set_prototype(&prototype);
 }
 
 Error::~Error()